ELECTRONIC DEVICE WITH CONNECTION BUMPS
Flip-chip electronic devices (40, 70, 80, 90) employ bumps (42, 72, 82) for coupling to an external substrate. Device cells (43, 73, 83, 93) and bumps (42, 72, 82) are preferably arranged in clusters (46) where four bumps (42, 72, 82) substantially surround each device cell (43, 73, 83, 93) or form a cross with the device cell (43, 73, 83, 93) at the intersection of the cross. The bumps (42, 72, 82) are desirably spaced apart by the minimum allowable bump (42, 72, 82) pitch (Lm). Typically, each device cell (43, 73, 83, 93) contains one or more active device regions (44, 74, 86, 96) depending on the overall function. Complex devices (40, 70) are formed by an X-Y array of the clusters (46), where adjacent clusters (46) may share bumps (43, 73, 83, 93) and/or device cells (43, 73, 83, 93). In a preferred embodiment, the bumps (42, 82) form the outer perimeter (48) of the device (40, 80, 90). The maximum device temperature and overall noise is reduced.
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The present invention generally relates to electronic structures, and more particularly relates to electronic structures and devices employing connection bumps.
BACKGROUNDMany electronic devices utilize solder bumps or the like for attachment and interconnection to a circuit board or other mounting structure. Flip-chip semiconductor devices are a common example. Such devices may comprise a single element or a small number of elements, or a complex arrangement of elements in an integrated circuit or in circuits of intermediate complexity. Such flip-chip devices usually are provided with solder bumps or equivalent during wafer processing. As used herein, the words “bumps” and “solder bumps” are intended to include bumps formed using any type of conductor with or without solder. Such bumps protrude from the surface of the semiconductor or other die. When the semiconductor or other die is to be coupled to its supporting substrate it is flipped over so that the bumps face toward the substrate and line up with mating attachment pads to which they are attached, e.g., by soldering. This is well known in the art. The composition and method of formation of the bumps themselves is outside the scope of the present embodiments.
The performance of such flip-chip devices, whether of semiconductor or other types of elements, depends critically on the placement of the bumps relative to the active regions and other elements on the die. In many prior art flip-chip devices, the placement of the bumps has focused more on their use for electrical coupling and less on their potential use for thermal coupling, that is, for removing heat from the chip. As a consequence, the electrical and thermal performance of such bumped devices is often less than desired. Accordingly, there is a need for improved device structures employing bumps that can provide improved performance, especially thermal performance. It is desirable to provide devices employing attachment/connection bumps that offer, for example, reduced operating temperatures without a significant increase in the total occupied area. Further, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the invention. Additionally, elements in the drawings figures are not necessarily drawn to scale. For example, the dimensions of some of the elements or regions in some of the figures may be exaggerated relative to other elements or regions of the same or other figures to help improve understanding of embodiments of the invention.
The terms “first,” “second,” “third,” “fourth” and the like in the description and the claims, if any, may be used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of use in sequences other than those illustrated or otherwise described herein. Furthermore, the terms “comprise,” “include,” “have” and any variations thereof, are intended to cover non-exclusive inclusions, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The terms “left,” right,” “in, out,” “front,” “back,” “up,” “down, “top,” “bottom,” “over,” “under,” “above,” “below,” ” “horizontal,” “vertical,” “diagonal,” and the like in the description and the claims, if any, are used for describing relative positions and not necessarily for describing permanent positions in space. It is to be understood that the embodiments of the invention described herein may be used, for example, in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner. The present invention does not depend upon the type of semiconductor material used for creating the various elements making up the electronic devices described herein, nor is it essential that the structures or devices described herein include semiconductor materials.
In this example, the bumps have the same diameter and are separated by horizontal spacings LH1, LH2, LH3, vertical spacings LV1, LV2, and diagonal spacings LD, etc., collectively spacings L. It is common to require that L not be smaller than a predetermined minimum value Lm, referred to as the minimum bump pitch. This is to insure that when device 20 is inverted, mounted on its mating circuit board and attached, e.g., by soldering the bumps to their mating pads, that shorts do not develop between the pads, for example by solder bridging. The minimum bump pitch Lm (i.e., the minimum center-to-center spacing) will depend on the bump diameter d (or equivalent lateral dimension for non-circular bumps). Currently, Lm is about 200 micrometers for bumps of about d=105 to 125 micrometers, preferably about 115 micrometers, but the particular values of Lm and d are not critical to the present invention. Larger or smaller values could also be used, provided that solder bridging or the like is avoided. It will be understood that the bumps cannot be placed arbitrarily close together but must, for practical reasons have some minimum separation Lm−d. With d=115 micrometers and Lm=200 micrometer, device 20 has 27 bumps, 2×72 device fingers of about 5760 square micrometers emitter area and the overall device occupies about 1.1 sq mm.
One of the difficulties associated with such bump-device layouts is that the operating temperature distribution within device 20 can be highly non-uniform.
It has been observed that only bumps 215, 225, 235 are in close enough proximity to device cells 211-213, 221-223, 231-233 to provide efficient heat exaction from the active regions of the device cells. For convenience, these eighteen bumps 215, 225, 235 are referred to as “thermal” bumps even though they may also have electrical functions. Bumps 216-217, 226-227, 236-237 are further away from device cells 211-213, 221-223, 231-233 and while they may be useful for electrical connections, they are not optimally disposed for efficient heat extraction. Thermal bumps typically connect from the device ground metal to the chip or die substrate.
The performance of device 40 is superior to that of device 20 in several respects.
While clusters 46 are illustrated in
It has been found that the arrangement illustrated in
Referring again to
According to a first embodiment, there is provided a flip-chip electronic device, comprising, multiple device cells having one or more active elements therein, multiple bumps adapted to thermally couple the device cells to an external substrate, and wherein the bumps and device cells are arranged so that four bumps substantially form a compact cluster around each device cell and the device comprises an X-Y array of such clusters. In a further embodiment, sharing of bumps or device cells between some adjacent clusters is allowed. In a still further embodiment, the bumps are spaced apart at least by the minimum allowed bump pitch. In a yet further embodiment, an outer perimeter of the device is formed by bumps spaced-apart by a minimum allowed bump pitch. In a still yet further embodiment, the cluster has diagonals and a principal direction of the cells is aligned with one of the diagonals. In a yet still further embodiment, the bumps and device cells are arranged in clusters wherein the four bumps substantially form a cross with the four bumps at ends of arms of the cross and with the device cell at the intersection of the arms of the cross and wherein a principal direction of the device cell is aligned with one of the anus of the cross. In another embodiment, the clusters are substantially square.
According to a second embodiment, an electronic device is provided, comprising, an array of device cells, and an array of bumps disposed so that four bumps surround each device cell in substantially equal thermal communication with the surrounded device cell. In a further embodiment, the four bumps are arranged so that lines drawn between pairs of bumps form arms of a cross and the device cell is located at the intersection of the arms of the cross. In a still further embodiment, the device cells comprise multiple active elements. In a yet further embodiment, at least some of the device cells comprise at least two active elements and at least two ballast resistors, whose long dimensions are aligned parallel to a first arm of the cross. In a still yet further embodiment, the at least two active elements are located closer to bumps on the second arm of the cross than the ballast resistors.
According to a third embodiment, there is provided an electronic device, comprising, multiple device cells, each device cell having an axis, multiple bumps disposed so that each device cell has first and second bumps thermally disposed on opposite sides of the device cell substantially on the axis thereof, thereby forming a cluster, and wherein at least a portion of the device comprises a parallel array of adjacent clusters, staggered so that a bump of one cluster is disposed next to a device cell of an adjacent cluster. In a further embodiment, the bumps of each cluster are separated by at least the minimum allowed bump spacing. In a still further embodiment, the clusters are arranged so that bumps form an exterior perimeter of the device. In a yet further embodiment, the clusters are arranged so that the bumps form an exterior boundary of the device on at least two sides thereof. In a still yet further embodiment, the parallel array of such clusters with a bump of one cluster disposed next to a device cell of an adjacent cluster has bumps of adjacent clusters substantially equally spaced. In a yet still further embodiment, clusters are serially arranged along a common axis to form lines of clusters arranged adjacent to each other but longitudinally displaced by approximately one-third the length of the cluster. In another embodiment, a perimeter of the device is formed by bumps on at least two sides thereof. In yet another embodiment, at least some of the multiple device cells comprise two active regions and two ballast resistors, wherein the two active regions are located closer to the bumps of the cluster than the ballast resistors.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist, especially with respect to choices of device types and materials, the number of active device fingers or other dissipating elements in each device cell and so forth. The above-described invention is especially useful for formation of semiconductor devices such as power amplifiers, but persons of skill in the art will understand based on the description here in that other types of devices can also be fabricated using the principles described herein, and that the invention is not limited merely to the examples presented for purposes of explanation. For example, and not intended to be limiting, the present invention is useful for fabrication of integrated passive devices, electro-optic devices, small signal devices, digital and analog devices, and combinations thereof on semiconductor and other substrates. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.
Claims
1. A flip-chip electronic device, comprising:
- multiple device cells having one or more active elements therein;
- multiple bumps adapted to thermally couple the device cells to an external substrate; and
- wherein the bumps and device cells are arranged so that four bumps substantially form a compact cluster around each device cell and the device comprises an X-Y array of such clusters.
2. The device of claim 1. wherein sharing of bumps or device cells between some adjacent clusters is allowed.
3. The device of claim 1, wherein the bumps are spaced apart at least by the minimum allowed bump pitch.
4. The device of claim 1, wherein an outer perimeter of the device is formed by bumps spaced-apart by a minimum allowed bump pitch.
5. The device of claim 1, wherein the cluster has diagonals and a principal direction of the cells is aligned with one of the diagonals.
6. The device of claim 1, wherein the bumps and device cells are arranged in clusters wherein the four bumps substantially form a cross with the four bumps at ends of arms of the cross and with the device cell at the intersection of the arms of the cross and wherein a principal direction of the device cell is aligned with one of the arms of the cross.
7. The device of claim 1, wherein the clusters are substantially square.
8. An electronic device, comprising:
- an array of device cells; and
- an array of bumps disposed so that four bumps surround each device cell in substantially equal thermal communication with the surrounded device cell.
9. The device of claim 8, wherein the four bumps are arranged so that lines drawn between pairs of bumps form arms of a cross and the device cell is located at the intersection of the arms of the cross.
10. The device of claim 9, wherein the device cells comprise multiple active elements.
11. The device of claim 10, wherein at least some of the device cells comprise at least two active elements and at least two ballast resistors, whose long dimensions are aligned parallel to a first arm of the cross.
12. The device of claim 11, wherein the at least two active elements are located closer to bumps on the second arm of the cross than the ballast resistors.
13. An electronic device, comprising:
- multiple device cells, each device cell having an axis;
- multiple bumps disposed so that each device cell has first and second bumps thermally disposed on opposite sides of the device cell substantially on the axis thereof, thereby forming a cluster; and
- wherein at least a portion of the device comprises a parallel array of adjacent clusters, staggered so that a bump of one cluster is disposed next to a device cell of an adjacent cluster.
14. The device of claim 13, wherein the bumps of each cluster are separated by at least the minimum allowed bump spacing.
15. The device of claim 13, wherein the clusters are arranged so that bumps form an exterior perimeter of the device.
16. The device of claim 13, wherein the clusters are arranged so that the bumps form an exterior boundary of the device on at least two sides thereof.
17. The device of claim 13, wherein the parallel array of such clusters with a bump of one cluster disposed next to a device cell of an adjacent cluster has bumps of adjacent clusters substantially equally spaced.
18. The device of claim 13, wherein clusters are serially arranged along a common axis to form lines of cluster arranged adjacent to each other but longitudinally displaced by approximately one-third the length of the cluster.
19. The device of claim 18, wherein a perimeter of the device is formed by bumps on at least two sides thereof.
20. The device of claim 13, wherein at least some of the multiple device cells comprise two active regions and two ballast resistors, wherein the two active regions are located closer to the bumps of the cluster than the ballast resistors.
Type: Application
Filed: Feb 5, 2007
Publication Date: Aug 7, 2008
Patent Grant number: 7683483
Applicant: FREESCALE SEMICONDUCTOR, INC. (Austin, TX)
Inventors: Radu M. Secareanu (Phoenix, AZ), Suman K. Banerjee (Tucson, AZ), Olin L. Hartin (Phoenix, AZ), Sandra J. Wipf (Phoenix, AZ)
Application Number: 11/671,048
International Classification: H01L 23/48 (20060101); H01L 29/00 (20060101);